One of the most fun and interesting science experiments around. Ferrofluid is a magnetic liquid that takes the shape of any magnetic field applied to it, and changes in density (it gets thicker) in a magnetic field. It's an AMAZING tool for visualizing magnetic fields in three dimensions! With a bottle of ferrofluid and some strong magnets, you'll be set for hours of fun experiments and demonstrations. The bottles we offer contain 50cc (a bit over an 1.5oz)